Blade of a wind turbine

ABSTRACT

A blade of a wind turbine is provided. The blade includes different layers, which are used to build up the three-dimensional shape of the blade. Resin is applied to connect the layers while the blade is manufactured. A reinforcement structure is arranged close to the surface of the blade and at a resin-rich-section of the blade, where a certain amount of resin is gathered during the manufacture of the blade.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority of European Patent Office applicationNo. 10163580.3 EP filed May 21, 2010, which is incorporated by referenceherein in its entirety.

FIELD OF INVENTION

The invention relates to a blade of a wind turbine

BACKGROUND OF INVENTION

Modern blades of a wind turbine are manufactured typically by help ofthe so called “Vacuum Assisted Resin Transfer Moulding, VARTM” process.

For this process a number of layers, which contain fibers, mats,balsa-wood, prefabricated components, balloons filled with any kind ofshaping material, . . . , etc. is put onto a so called “lower mould” tobuild up the three-dimensional shape of the blade. The lower mould isused to support the “sandwich structure” of the blade.

The lower mould is connected with an “upper mould” to form a closedmould structure. The moulds enclose or better encapsulate the bladestructure.

During the VARTM-process a technical vacuum is applied to the closedmould structure, thus air is evacuated out from this structure whileresin is infused into the structure accordingly.

The resin is allowed to cure out and the blade can be removed from thedismounted moulds.

The VARTM-process allows the production of very strong blades and ofvery strong composites and components.

The composites and components may be designed and constructed to belocated inside a blade later, while the blade is manufactured in asubsequent VARTM-process.

The products, which are manufactured by help of the VARTM-process, evenshow a reduced weight due to the balsa-wood and due to balloons used.The balloons stay inside the product while it is manufactured, but willbe removed later, thus a kind of an air-filled cavity remains inside theproduct.

The most part of the product, especially of the manufactured blade, isbuilt up reinforcing materials, especially by glass-fibers, carbonfibers, woven mats, etc.

Within this VARTM-process a problem arises. The closed mould system maycontain deep and concave-shaped cross-sections and areas, which areneeded to build up the specific and needed shape of the product.

For example the trailing edge and/or the leading edge belong to thosesections.

Fiber mats, which are used to build up the shape of the section, may notbe aligned close and firm to an intended surface of the blade. Theintended surface is determined by the curvature of the inner surface ofthe later closed mould system.

During the build-up process of the blade the fiber mats might follow acurvature which is different to the intended one. For example the fibermats may tend to a shape like catenaries (hanging chain) in certaincircumstances.

This effect results in a number of voids, which are located between theinner surface of the closed mould system and the fiber mats. Due to theVARTM process the voids will be filled with resin.

In this case the weight of the blade is increased due to the weight ofthe resin, while the structure of the blade might be weakened by theresin, as the resin shows no inner support structure (fibers) at theseslocations. Cracks may be the result on the blade surface.

The wind turbine blade is exposed to fatigue load, thus the leading edgeand the trailing edge of the blade may show fatigue-cracks in the bladesurface.

Cracks need to be repaired by hand. This work is time consuming andexpensive.

SUMMARY OF INVENTION

It is therefore the aim of the invention, to provide an improved windturbine blade to overcome the problems mentioned above.

This aim is reached by the features of the claims.

Preferred embodiments of the invention are object of the dependentclaims.

According to the invention the blade of a wind turbine containsdifferent layers, which are used to build up the three-dimensional shapeof the blade. Resin is applied to connect the layers while the blade ismanufactured. A reinforcement structure is arranged close to the surfaceof the blade and at a resin-rich-section of the blade, where a certainamount of resin is gathered during the manufacture of the blade.

According to the invention the reinforcement structure is a shaped andpreferably open laminate, which is arranged at sections of the blade,where a big amount of resin will usually arise, for example during anapplied VARTM process.

These sections contain sharp corners of the blade for example, like thetrailing edge or like the leading-edge of the blade.

Due to the invention the production of the blade is cheaper, as thenumber of cracks are minimized or even avoided due to the reinforcementstructure. Thus the repair-work is reduced or even avoided.

Due to the invention the weight of the blade is reduced as the number ofresin-filled-voids is even reduced.

Due to the invention the blade structure, especially the leading and thetrailing edge, is stronger. Resin-rich areas are supported by thereinforcement structure, which is an integrated part of the blade.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is shown in more detail by help of figures now.

The figures show preferred embodiments and do not limit the scope of theinvention.

FIG. 1 shows the arrangement invented by help of a cross-sectional viewto a closed-mould-system,

FIG. 2 shows the shape of the “open grid laminate”, which is used anddescribed in FIG. 1.

FIG. 1 shows the arrangement invented by help of a cross-sectional viewto a part of a closed-mould-system. CMS.

A lower mould LM is used within a VARTM-process to support the blade BLof a wind turbine.

The structure of the blade BL is built up by fibers, mats, balsa-wood,prefabricated components, balloons filled with any kind of shapingmaterial, . . . , etc. (not shown here in detail) as described above.Thus these elements form different layers of the wind turbine blade.

Thus the lower mould LM is used to support this “sandwich structure” ofthe blade BL.

An upper mould UM is connected with the lower mould LM and is also usedto build up the closed-mould-structure as described above.

The cross sectional view shows the trailing edge TE of the blade BL.

Due to the inner surface IS of the closed-mould-structure and due to thespecific shape of the trailing edge TE a resin rich area RRA will becreated.

If no further steps are taken the VARTM-process would lead to cracks, asdescribed above and will lead to voids. The voids might be locatedbetween the inner surface IS of the closed mould structure and thesurface of the blade BL (or better and the fiber-mat-surface of theblade BL) along the trailing edge TE.

To overcome these problems a shaped laminate structure SLS is used asreinforcement structure. It is located along the trailing edge TE andwithin the resin rich area RRA.

Preferably the shaped laminate structure SLS is shaped like a rail,showing an angle in its cross section.

The angle is chosen in a way that the shaped laminate structure SLS,used as reinforcement structure, is attached in a form-fit-manner to thelayers of the blade.

The angle might be a right angle with 90°, for example.

Preferably the shaped laminate structure SLS is made as an openstructure, like a grid. This allows that resin penetrates the laminatestructure SLS during the VARTM process.

When the VARTM process is applied and when the blade BL is finished theshaped laminate structure SLS is an integrated part of the blade BL.

As the resin gets inside the shaped laminate structure SLS it is used asa reinforcement-structure inside the blade BL.

Preferably the shaped laminate structure SLS is made as pre-casted openstructure. The pre-casted structure is integrated and fixed by the resinwithin the blade BL.

The arrangement invented minimizes the need for post-repairs.Additionally the manual work during the lay-up process of the bladeelements (fiber, mats, wood, etc.) is easier than before as the “hangingchain” effect as described above is reduced.

Thus an easier and simplified lay-up of the fiber material at sharpcorners of the blade is allowed. It is even possible to implement and toachieve more difficult curvatures for the shape of the blade.

Preferably the shaped laminate structure SLS is arranged close to thesurface of the blade BL.

The shaped laminate structure SLS is used as an edge-protection,especially for the trailing edge and/or for the leading edge or otherrelevant sections of the blade BL.

FIG. 2 shows the shape of an open grid laminate OGL, which is used asshaped laminate structure SLS according to FIG. 1.

1.-10. (canceled)
 11. A blade of a wind turbine, comprising: a pluralityof different layers, which are used to build up a three-dimensionalshape of the blade; and a reinforcement structure, which is arrangedclose to a surface of the blade and at a resin-rich-section of theblade, wherein resin is applied to connect the plurality of layers whilethe blade is manufactured, and wherein a certain amount of resin isgathered at the reinforcement structure during the manufacture of theblade.
 12. The blade according to claim 11, wherein the reinforcementstructure is arranged along at least a part of the trailing edge, andwherein the reinforcement structure is arranged along at least a part ofthe leading edge, and wherein the reinforcement structure is arrangedclose to a plurality of sharp corners of the blade.
 13. The bladeaccording to claim 11, wherein the reinforcement structure is arrangedalong at least a part of the trailing edge.
 14. The blade according toclaim 11, wherein the reinforcement structure is arranged along at leasta part of the leading edge.
 15. The blade according to claim 11, whereinthe reinforcement structure is arranged close to a plurality of sharpcorners of the blade.
 16. The blade according to claim 11, wherein theblade is manufactured by an applied Vacuum Assisted Resin TransferMoulding process, which uses a closed-mould-structure to encapsulate theblade while the resin is applied.
 17. The blade according to claim 16,wherein the resin-rich-section is defined by an inner surface of theclosed-mould-structure and by the shape of the blade.
 18. The bladeaccording to claim 11, where the reinforcement structure is a rail. 19.The blade according to claim 11, wherein the reinforcement structureincludes an angle in its cross section, while the angle is chosen in away that the reinforcement structure is attached in a form-fit-manner tothe plurality of layers of the blade.
 20. The blade according to claim19, wherein the angle is 90°.
 21. The blade according to claim 11,wherein the reinforcement structure is a laminate structure and apre-casted laminate structure.
 22. The blade according to claim 11,wherein the reinforcement structure is a laminate structure.
 23. Theblade according to claim 11, wherein the reinforcement structure is apre-casted laminate structure.
 24. The blade according to claim 11,wherein the reinforcement structure comprises a plurality of channels ortubes, and wherein the applied resin penetrates the reinforcementstructure.
 25. The blade according to claim 11, wherein thereinforcement structure is an integrated part of the blade.
 26. Theblade according to claim 24, wherein the reinforcement structure is anintegrated part of the blade.
 27. The blade according to claim 26,wherein the reinforcement structure is arranged close to a surface ofthe blade.